1. Field of the Invention
This invention relates generally to athletic equipment and more particularly to inserts for the finger holes of bowling balls.
2. Description of the Prior Art
A bowling ball is provided with a pair of finger holes and a thumb hole. The finger holes of the bowling ball are adapted to receive the two center fingers of a bowler's hand.
Depending on the spacing between the finger holes and the thumb hole of the bowling ball, the bowler's middle fingers are inserted into the finger holes to the depth of either the first finger joint or the second finger joint. Most skilled bowlers use bowling balls which only allow the first finger joint of the bowler's hand to be inserted into the finger holes. This is known as the "finger tip grip" configuration for a bowling ball, and affords maximum power and control over the ball.
A problem with finger tip grips for bowling balls is that the frictional engagement area between the finger tip and the finger hole is small, requiring a tighter compressive grip by the bowler to properly hold and release the ball. To offset this problem, a number of finger hole inserts for bowling balls have been invented.
In U.S. Pat. No. 4,358,112 of Straborny, a finger hole insert for bowling balls is disclosed which includes a tubular member having a thickened wall portion provided with a slot. The slot facilitates the entry of air into the finger hole and reduces the problem of vacuum caused by the rapid removal of the fingers from the insert during the release of the ball.
In U.S. Pat. No. 4,432,546 of Allen, Jr. an insert is described having a high friction, corrugated surface which enhances the grip of the finger tip. The finger opening of the insert can be adjusted for various finger sizes.
Bach in U.S. Pat. No. 3,784,198 teaches a finger hole liner provided with a key-like ridge adapted to lock to a keyway or circumferential groove formed within the finger hole of a bowling ball. The finger hole of Bach's liner is substantially elliptical.
Similar finger hole inserts can be found in U.S. Pat. No. 4,381,863 of Norman, U.S. Pat. No. 580,207 of Boemermann et al., U.S. Pat. No. 2,469,268 of Jerome, U.S. Pat. No. 2,646,985 of Nagy et al., U.S. Pat. No. 2,482,190 of Kramer, and U.S. Pat. No. 4,289,312 and U.S. Pat. No. 4,416,452 both of Heimbigner.
All of the above cited patents teach finger hole inserts having a generally cylindrical outer surface and an inner surface adapted to engage a bowler's finger tip. The prior art inserts generally include an internal surface configuration or lip configuration which engages the bowler's finger tip to provide enhanced frictional contact between the finger tip and the insert. This enhanced frictional engagement is active throughout the entire swing and release of the bowling ball.
A problem that the prior art does not address is the fact that increased frictional engagement between the finger tip and the bowling ball insert is not desirable at all points of the swing and release of the ball. For example, the frictional engagement between the finger tip and the insert should be minimized at the time of release of a ball so that the bowling ball can be easily and smoothly released.